Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$17.81	3.518%	$18.4366	$18.44	$18.45	$18.40
Purchase #2	$208.47	5.625%	$220.1964	$220.20	$220.20	$220.20
Purchase #3	$78.47	13.732%	$89.2455	$89.25	$89.25	$89.20
Purchase #4	$71.36	8.187%	$77.2022	$77.20	$77.20	$77.20
Purchase #5	$223.75	13.472%	$253.8936	$253.89	$253.90	$253.90
Purchase #6	$244.34	4.636%	$255.6676	$255.67	$255.65	$255.70
Purchase #7	$83.89	4.658%	$87.7976	$87.80	$87.80	$87.80
7 purchase totals =	$928.09		$1,002.4395	$1,002.45	$1,002.45	$1,002.40